Allogeneic hematopoietic transplantation induces clinically relevant B-cell responses to minor histocompatibility antigens (mHA). In contrast to T cell immunity, it is relatively easy to characterize B-cell responses, antibodies, to specific antigens in large patient cohorts. To test this, we developed ELISA to detect antibody responses against mHA encoded by the Y-chromosome, called H-Y antigens. Our research demonstrates 50% of male transplant patients with female donors (F cGVHD development (p<0.0001). In addition, we found that 30-40% of normal females have low-titer anti-H-Y antibodies, while normal males have essentially none. Our proposed research will determine whether the bone marrow of anti-H-Y antibody positive donors transfers H-Y-specific GVHD and/or GVT immunity to their recipients. The National Marrow Donor Program (NMDP) provided sera from 520 female donors who provided bone marrow grafts for HLA-identical male recipients, their paired clinical information, and follow-up sera sample from the 145 surviving male recipients to directly test if paired female donors and male recipients develop antibodies against shared H-Y peptide epitopes. In this study, we plan to introduce proteomic microarrays to facilitate our investigation of allogeneic antibody responses in human transplantation. HYPOTHESIS: In sex-mismatched transplantation, bone marrow collected from female donors with anti-H-Y antibodies will transfer strong B cell responses specific for H-Y antigens. The clinical outcome of H-Y allogeneic immune responses is correlated to the specificity of anti-H-Y antibody responses and the H-Y protein /antigenic determinants that are targeted in the female donor and male recipient. Technology Aim: Develop H-Y microarray technology to improve detection sensitivity and fine specificity analysis of serum antibodies to H-Y proteins and their overlapping peptides. Aim 1 Determine the prevalence and specificity of antibody to H-Y antigens in 500 healthy female donors in relation to donor age and parity. Aim 2 Determine if male patients receiving bone marrow grafts from females with H-Y antibody have different clinical outcomes than males with H-Y sero-negative female donors. Aim 3 Determine if male patients develop allogeneic antibodies against the same H-Y antigens and peptide epitopes as their female donors. SIGNIFICANCE: The microarray platform multiplexes and increases the sensitivity of allogeneic antibody detection for clinical correlation. Hypothesis validation supports improved HCT donor selection by directly measuring their H-Y antibodies in F Allogeneic antibody develops against H-Y antigen in 50% of male HCT patients with female donors and is strongly associated with chronic GVHD development. Sera from 520 normal female donors will be tested by microarray technology for antibodies against a panel of H-Y proteins and hundreds of composite H-Y peptide epitopes. Female donor H-Y reactivity will be correlated with male recipient clinical outcomes, and male recipient H-Y antibody epitope specificity thereby testing an H-Y B cell adoptive transfer hypothesis. [unreadable] [unreadable] [unreadable]